Velocity and Temperature Profiles in Turbulent Channel Flow at Supercritical Pressure

Abstract

Understanding the effects of property variations on velocity and temperature profiles is important for the accurate prediction of supercritical heat transfer in regenerative cooling channels. In this study, direct numerical simulations of a planar turbulent channel flow with a wall-normal temperature gradient were conducted to understand the mean temperature profiles that are affected by property variations at supercritical pressure. The working fluid used was supercritical nitrogen. The density ratios between two walls were four and eight. The Van Driest transformation for the mean velocity profiles holds true in the present conditions. This result implies that discussions based on a mixing length hypothesis are valid for the conditions that were studied. Mean temperature profiles in the viscous sublayer are correlated to those of incompressible constant-property flows using a local Prandtl number. For the mean temperature profiles in the logarithmic region, a new temperature transform equation that accounts for the variation in mean density and isobaric specific heat was introduced. It was demonstrated that the gradients of temperature profiles transformed by the transform equation coincide with the ones in incompressible constant-property flows in the logarithmic region.